Dynamic priority based message transmitting apparatus, priority adjusting apparatus using the same, and dynamic priority message processing method

ABSTRACT

A dynamic priority based message transmitting apparatus includes a priority storing block for recording priorities in a communication network environment having multitude nodes and recording the lowest priority among the priorities, a communication bus monitoring block for monitoring a communication bus and transmitting its message when the communication bus is available, a message collision solving block for solving message collision by monitoring message transmission when messages are transmitted from the other nodes simultaneously, comparing its priority and those of the other nodes and, as the comparison result, transmitting its message if its priority is higher than those of the other nodes while not transmitting its message if otherwise, a message filtering block for executing filtering by judging whether or not its node has to process a certain message based on an identifier of the certain message, and a priority adjusting block for adjusting its priority according to a predefined rule.

FIELD OF THE INVENTION

The present invention relates to a dynamic priority based messagetransmitting apparatus, a priority adjusting apparatus using the messagetransmitting apparatus and a dynamic priority message processing methodcapable of making each of nodes send and receive data anytime accordingto its priority when the nodes try to send and receive data to eachother in an environment consisting of the nodes and transmission media(communication bus).

DESCRIPTION OF RELATED ART

In case of vehicles, there are various control systems such as anelectric mirror adjusting device, a sunroof, a power window, a seatcontrol device, various instruments, stability control like an anti lockbrake system (ABS), engine maintenance, gearshift and so on. A wiringdevice, which connects and controls these complicated distributedcontrol systems, requires a multiplicity of cables and this occupies asubstantial portion of kerb weight and manufacturing cost.

In order to overcome the above shortcomings, like a local area network(LAN) scheme for connecting desk-top personal computers (PC) in anoffice, there is being adopted a scheme of connecting the controlsystems with one common communication bus and performing messagetransmission through the common communication bus. This scheme reducesthe total manufacturing cost and an amount of wiring in a vehicle.

For instance, when a driver presses on a brake pedal so as to reduce avehicle's speed, a sensor attached to the brake pedal detects thestrength of the brake pedal pressed and delivers the detected strengthto a brake pedal control system. Then, the brake pedal control systemtransmits the detected strength to a brake control system through acommon network bus to drive a brake.

Recently, many vehicle systems are adopting a scheme which connects andcontrols systems such as controllers, sensors, actuators and so onthrough a communication network.

A mobile robot driven by wheels includes a wheel driver and a controllerfor detecting its location and obstacles by using various sensors, e.g.,an infrared sensor and a sonar sensor, and controlling its motion toavoid the obstacles and reach to a destination. Nowadays, acommunication scheme using the common communication bus described aboveis used to connect various sensors, controllers and drivers in therobot. Specially, a humanoid robot necessarily adopts the abovecommunication scheme since it is formed with a plurality of sensors,controllers and drivers.

There is a controller area network (CAN) as the technology whichconnects the distributed control systems and is mostly used for themessage transmission between the distributed control systems. Moreover,recently, there is gradually spreading the technology such as atime-triggered CAN (TTCAN), a time-triggered protocol (TTP) and FlexRay.

* CAN (Controller Area Network)

The CAN is an automotive network system developed in 1988 by Bosch Groupand Intel Corporation to perform the digital serial communicationbetween measurement and control equipments in a vehicle. The CAN wasinternationally standardized in 1993 as ISO 11898 (for high-speedapplications) and ISO 11519 (for low-speed applications). A CAN bus wasdesigned for the communication between microcontrollers and isapplicable to functions of high-speed, high noise immunity and errordetection.

The CAN bus is widely used in manufacturing industry and aerospaceindustry in addition to the automotive industry. In a field of theautomotive industry, it is usually used to perform information exchangebetween electronic control units (ECU) such as an engine maintenancesystem, a gearshift controller, an instrument pack, electronictechnology for a vehicle body and so on.

In the CAN, message transmission between two nodes is performed by aproducer-consumer scheme unlike node-oriented transmission recording anaddress of a node, which will receive a message, in the message. Amessage transmitted by a producer node is delivered to all of otherconsumer nodes. In this case, instead an address of a node, which willreceive the message, is not recorded in the message; the node receivesthe message through a message identifier. The node receiving the messagecan selectively receive the message by using a filtering function on aCAN protocol controller chip hardware. When transmitting messages to allnodes on a network, it is referred to as broadcasting.

The CAN adopts a CSMA/CD-NDBA (Carrier Sense Multiple Access withCollision Detect Non-Destructive Bitwise Arbitration) scheme. That is,the CAN, which is always monitoring a bus, transmits data only when theCAN bus is in an idle state. The CAN detects collision when there aremore than 2 nodes connecting to the CAN bus to transmit data at the sametime and transmits a message whose priority is higher than others, tothereby avoid data loss. Therefore, since only the message whosepriority is higher is transmitted in case of the CAN, when an amount ofmessages to be transmitted becomes large, there occurs a situation wherea message whose priority is lower is always in a waiting state withoutbeing transmitted. Namely, the reliability of the CAN substantially goesdown in a network environment having lots of messages to be transmitted.

* TTP (Time-Triggered Protocol)

The TTP was developed by a Brite Euram project “X-by-wire” and an ESPRITOMI project “TTA” of the Technical University of Vienna. After theprojects were terminated, TTA regulations were transferred to TTTech(http://wwww.tttech.com).

The TTP is based on a TDMA (Time Division Multiple Access) scheme. TheTTP is a protocol of dividing a material transmission time to have acertain time width, assigning the divided time to each node subsequentlyand making each node transmit data only within the time width. Forexample, if there are 3 nodes A, B and C, the node A transmits data atfirst and, then, the nodes B and C transmit data subsequently. If thenode A′ turn comes round, the node C has to wait for its turn althoughit wants to transmit data.

In the TTP, it is predictable when data of each node are transmittedand, moreover, a minimum delay time of the data is guaranteed. However,although a certain node only has data and other nodes do not have datato be transmitted, the certain node has to wait for its turn. As aresult, a total amount of data transmitted becomes smaller than that ofthe CAN.

However, since the TTP guarantees the minimum delay time when the dataof the certain node are transmitted, it can be used in a system forcedto have safety such as a brake control system and an airbag system of avehicle.

Like the TTP, a scheme where a fixed node sends messages at a certaintime is referred to as a time-triggered system. On the other hand, likethe CAN, a scheme of sending messages instantly if there is a nodehaving data to be transmitted is referred to as an event-triggeredsystem.

Lately, there is emerging a protocol such as TTCAN and FlexRay, whichare formed by mixing the time-triggered system and the event-triggeredsystem.

* TTCAN (Time-Triggered Controller Area Network)

The TTCAN is a protocol implementing the time-triggered technology basedon the CAN.

A major feature of the TTCAN is to control data transmission through theTDMA like a method of using a timely regular repeated cycle referred toas a basic cycle. The basic cycle consists of 4 types of windows such asa reference message, an exclusive window, an arbitration window, a freewindow, etc.

Herein, the reference message is transmitted by a global time master andrepresents the start of the basic cycle.

The exclusive window is constructed with a time slice having the lengthas long as accommodating data and messages to be transmitted, andprepared for one certain CAN message.

In the arbitration window, several nodes can try to transmit messagesand the nodes trying to transmit messages compete with each other byusing a non-breakdown bitwise arbitration method like the CAN scheme.

Therefore, a node having the highest priority can transmit messages.

While a node defeated in the arbitration competition tries to retransmitmessages in the CAN system, the message retransmission is not permittedin the TTCAN since the retransmission breaks down the execution ofremaining parts of the basic cycle.

The TTCAN is a system formed by combining the time-triggered scheme andthe event-triggered scheme. It synchronizes the time of each site basedon the reference message, uses the time-triggered scheme in theexclusive window of the basic cycle and uses the event-triggered schemesimilar to the CAN in the arbitration window.

* FlexRay

Each node sending and receiving information in a communication networkshares transmission media (communication bus). The CAN protocol is basedon a principle of carrier sense multiple access (CSMA) and each nodemonitoring the bus transmits data instantly if the bus is available. Thecollision between nodes sending data at the same time is avoidedaccording to a priority rule.

The FlexRay is based on the TDMA. Each node or message is assigned to afixed time slot to which the node or message has exclusive access. Thetime slot is repeated at defined intervals. Each node can send messagesonly to a time slot assigned thereto. The time that the message is on abus is exactly predictable. However, when strictly assigning bandwidthsof the bus to nodes or messages corresponding to the fixed time slots,there is a defect that the bandwidths are not fully utilized. That is,when a certain node tries to send messages, it has to wait for a timeslot assigned thereto.

Therefore, the FlexRay divides a cycle to a static part and a dynamicpart. Fixed time slots exist in the static part and, in the dynamicpart, time slots are dynamically assigned.

Similarly to the TTCAN, the FlexRay operates in the time-triggered formof the TDMA in the static part while it operates in the event-triggeredform in the dynamic part.

In summary, in the TTCAN or FlexRay, the messages are separatelytransmitted according to a part adopting the time-triggered scheme likethe TTP and a part adopting the event-triggered triggered scheme likethe CAN. That is, there is not shown a scheme which dynamically changesthe priority of each node based on the event-triggered scheme and isalso mixed with the time-triggered scheme.

Moreover, in the TTCAN or the FlexRay, the message transmissionefficiency can be deteriorated in the part of adopting thetime-triggered scheme and the transmission of messages having lowerpriorities can be continuously delayed in the part of adopting theevent-triggered scheme.

Therefore, there is required a scheme for improving ineffective messagetransmission of the time-triggered scheme based on the event-triggeredscheme and overcoming the defect of the event-triggered scheme bydynamically adjusting the priority.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide adynamic priority based message transmitting apparatus, a priorityadjusting apparatus using the message transmitting apparatus and adynamic priority message processing method capable of guaranteeing aminimum transmission delay time of messages and making each of nodessend and receive data anytime according to its priority in anenvironment constructed with the plurality of nodes and transmissionmedia (communication bus).

In accordance with an aspect of the present invention, there is provideda dynamic priority based message transmitting apparatus, which includesa minimum priority storing block for recording priorities in acommunication network environment consisting of a plurality of nodes andrecording the lowest priority among the priorities, a communication busmonitoring block for monitoring a communication bus and transmitting acorresponding message when the communication bus is in an idle state, amessage collision solving block for solving message collision bymonitoring message transmission when messages are transmitted from theother nodes at the same time, comparing a corresponding priority andthose of the other nodes and, according to the comparison result,transmitting the corresponding message if the corresponding priority ishigher than those of the other nodes while not transmitting thecorresponding message if the corresponding priority is lower than thoseof the other nodes, a message filtering block for performing thefiltering by judging whether or not a corresponding node has to processthe corresponding message based on an identifier of the correspondingmessage, and a priority adjusting block for adjusting the priority ofthe corresponding node according to a predefined rule.

Herein, the priority adjusting block operates based on a local priorityadjusting scheme in which the priority adjusting block in each nodeadjusts the priority of the corresponding node every fixed time, or aglobal priority adjusting scheme in which the priority of thecorresponding node is adjusted only when receiving a priority adjustingmessage from a global priority adjusting device.

In accordance with another aspect of the present invention, there isprovided a global priority adjusting apparatus using a dynamic prioritybased message transmitting device, which includes a static/dynamicpriority adjusting table, and a priority adjusting message transmittingunit for delivering a priority adjusting message. Herein, the priorityadjusting message transmitting unit continuously sends the priorityadjusting message in a preset time period and the preset time beingstored in the static priority adjusting table while it sends thepriority adjusting message in an irregular period changing according toa time stored in the dynamic priority adjusting table and the time isdifferently set to each node on a communication network and stored inthe dynamic priority adjusting table.

In accordance with further another aspect of the present invention,there is provided a dynamic priority message processing method, whichincludes the steps of assigning a priority and a minimum priority toeach node in a communication network environment consisting of aplurality of nodes, checking out whether or not a current communicationbus is available according to a message transmission request from a userand, as a result of the comparison, transmitting a corresponding messageif the communication bus is available, detecting message collision ifmore than two nodes transmit messages at the same time through a messagecollision solving unit and transmitting a message of a node having thehighest priority after comparing priorities of the nodes, receiving onlya message which should be processed at a corresponding node receivingthe message by using a filtering function after the corresponding nodechecks identifier information of the message, and changing its priorityaccording to a preset time or adjusting the priority after receiving apriority adjusting message from a global priority adjusting device.

The present invention can perform a time-triggered message transmittingscheme and an event-triggered message transmitting scheme in acommunication network environment consisting of multitude nodes tryingto send and receive messages and a communication bus for thecommunication between the nodes.

Moreover, in accordance with present invention, it is possible toovercome the unpredictability of the message transmission time of theCAN protocol operating in the conventional event-triggered scheme andthe ineffectiveness of the total message throughput of the TTP operatingin the time-triggered scheme, assign a priority to each node andtransmit messages in an arbitrary time of each node. Also, although anode has a lower priority, the priority becomes higher by dynamicallychanging the priority of each node to thereby transmit messages of thenode. As a result, each node can send messages in an arbitrary time anda node having a higher priority can send messages by the adjustingprocess like the CAN when several nodes send messages at the same time.However, since the priority of each node is subsequently changedaccording to a predetermined rule, any node can send its messages whenits priority becomes higher after a specific time is passed. That is,any node having a lower priority can send its messages without waitingindefinitely.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the preferredembodiments given in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a constitutional view of showing the relationship between eachcontrol node and a global priority adjusting device in a communicationnetwork system in accordance with the present invention;

FIG. 2 shows a constitutional view of a dynamic priority based messagetransmitting device in accordance with the present invention;

FIG. 3 illustrates a view of explaining the global priority adjustingdevice in accordance with the present invention; and

FIG. 4 depicts a constitutional view of the global priority adjustingdevice using the dynamic priority based massage transmitting device inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Other objects and aspects of the invention will become apparent from thefollowing description of the embodiments with reference to theaccompanying drawings, which is set forth hereinafter.

FIG. 1 is a constitutional view of showing the relationship between eachcontrol node and a global priority adjusting device in a communicationnetwork system in accordance with the present invention.

As shown in FIG. 1, the inventive communication network system includesN numbers of nodes 10 communicating with each other, N being a positiveinteger, a global priority adjusting device 30 for sending a priorityadjusting message to each of the nodes 10 and a communication bus 20connecting the nodes 10 and the global priority adjusting device 30.

FIG. 2 shows a constitutional view of a dynamic priority based messagetransmitting device in accordance with the present invention.

In FIG. 2, the inventive message transmitting device (node 1) 10includes a priority storing unit 21 for recording its priority in acommunication network environment consisting of the plurality of nodes10, a minimum priority storing unit 22 for recording the lowest priorityamong the priorities stored in the priority storing unit 21, a messagetransmitting block 25 which has a communication bus monitoring unit 23for monitoring the communication bus 20 and transmitting messages whenthe communication bus 20 is in an idle state and a message collisionsolving unit 24 for solving message collision by monitoring messagetransmission when a message is transmitted through another node, e.g.,node 2, at the same time, comparing, likely to the CAN, the priority ofthe node 1 and that of the node 2 and, according to the comparisonresult, transmitting its message if the priority of the node 2 is lowerthan that of the node 1 while not transmitting its message if thepriority of the node 2 is higher than that of the node 1, a messagefiltering block 26 for performing the filtering by judging whether ornot the node 1 has to process a certain message based on an identifierof the certain message, and a priority adjusting block 27 for adjustingits priority according to a predefined rule.

Herein, the priority adjusting block 27 employs a local priorityadjusting scheme and a global priority adjusting scheme. According tothe local priority adjusting scheme, the priority adjusting block 27 ineach node adjusts the priority of its corresponding node every fixedtime. On the other hand, according to the global priority adjustingscheme, the priority of the corresponding node is adjusted only whenreceiving a priority adjusting message from the global priorityadjusting device 30.

At this time, the message consists of a message header having a messageidentifier, other control information, etc. and a message bodycontaining practical data to be transmitted.

Hereinafter, there will be explained in detail the operation of themessage transmitting device (node) based on the dynamic priority inaccordance with the present invention having the construction describedabove.

Each node transmits a message through the message transmitting block 25.The communication bus monitoring unit 23 in the message transmittingblock 25 monitors the communication bus 20 and, then, sends data if thecommunication bus 20 is in an idle state. If another node tries to senda message at the same time, the message collision solving unit 24detects it, compares priorities of the other node and its correspondingnode, sending its message if the priority of its corresponding node ishigher than that of the other node while not sending its message if thepriority of its corresponding node is lower than that of the other node.If one node sends a certain message, all nodes connected to thecommunication bus 20 receive the certain message. The message filteringblock 26 processes the certain message if the certain message isdetermined as a message, which its corresponding node has to process,based on an identifier of the certain message, and ignores the certainmessage if otherwise. Then, in case of using the global priorityadjusting scheme, if the message received through the message filteringblock 26 is the priority adjusting message, the message is delivered tothe priority adjusting block 27 to adjust the priority of thecorresponding node. On the other hand, in the event of using the localpriority adjusting scheme, the priority of the corresponding node isadjusted every fixed time.

FIG. 3 illustrates a view of explaining the global priority adjustingdevice 30 in accordance with the present invention.

As described in FIG. 3, the global priority adjusting device 30 is adevice for broadcasting the priority adjusting message to the pluralityof nodes at the same time and adopts a dynamic priority adjusting schemeand a static priority adjusting scheme.

Each node receiving the priority adjusting message adjusts its priority.When initializing the communication network, each node 10 stores itspriority and minimum priority information. The priority of the node 10is assigned with an integer, e.g., 1, 2, . . . , and it has a higherpriority when the number of the priority is lower.

At this time, the priority of the global priority adjusting device 30 isfixed to ‘0’ and not changed according to the dynamic priority scheme.

Therefore, the priority adjusting message according to the dynamicpriority scheme is delivered prior to other messages. The priorityadjusting message should be received by all nodes and its receivingshould not be refused by the filtering.

A minimum priority among the priorities of the node 10 is assigned tothe minimum priority storing unit 22 and, in this case, ‘N’ is storedtherein. If a certain node receives the priority adjusting message, itadds ‘1’ to its priority and the changed priority is stored at thepriority storing unit 21. If the changed priority is larger than thevalue stored at the minimum priority storing unit 22, the priority ofthe certain node is assigned to ‘1’. That is, if the certain nodereceive the priority adjusting message, it lowers its priority by onestep and, as a result, a node having the lowest priority is changed tohave the highest priority again. In this way, the priority of each nodedynamically varies and it returns to its initial priority after thedynamic priority change is repeated N times. If each node receives thepriority adjusting message (N-1) times, it can have the highest priorityat least one time and, thus, send its message without waitingindefinitely. Furthermore, it is more effective that, if a node having apriority higher than the certain node does not have messages to be sent,the certain node can send its message instantly without waiting unlikein the TTP.

The above dynamic priority adjusting method explains the global priorityadjusting scheme and it is applicable to the local priority adjustingscheme in the same way.

FIG. 4 depicts a constitutional view of the global priority adjustingdevice using the dynamic priority based massage transmitting device inaccordance with the present invention.

As illustrated in FIG. 4, the inventive global priority adjusting device30 broadcasts the priority adjusting message to the plurality of nodesat the same time and its priority adjusting message transmitting schemecan be classified to a static scheme and a dynamic scheme.

The static scheme sends the priority adjusting message in a constantperiod, i.e., a fixed time period, continuously and the fixed time isstored in a static priority adjusting table 31.

On the other hand, the dynamic scheme sends the priority adjustingmessage in an irregular period which is changed according to a timestored in a dynamic priority adjusting table 32. In general, the time isdifferently set to each node on the communication network and stored inthe dynamic priority adjusting table 32.

The above two schemes are examples for the dynamic priority adjustmentand it is obvious that the priority adjusting time can be controlled inother various schemes.

Hereinafter, there is explained in detail the operation of the globalpriority adjusting device using the dynamic priority based messagetransmitting device in accordance with the present invention.

At first, in the communication network environment consisting of theplurality of nodes, there are assigned a priority and a minimum priorityto each of the nodes.

Then, a user application sector trying to transmit messages sets amessage identifier and other control information to a message header andinputs practical message contents into a message body.

A node received a message transmission request from the user applicationsector checks out whether a current transmission bus is available or notand, according to the checking result, transmits a corresponding messagewhen the bus is available.

When more than two nodes send messages at the same time, only a nodehaving the highest priority is controlled to send its message and a nodereceiving the message checks out identifier information of the messageand, then, accepts the message only when the message should be processedby it using a message filtering function.

And then, the global priority adjusting device 30 sends a prioritychanging message to each node which subsequently changes its priorityaccording to a predetermined rule.

As described above, the present invention can be implemented as aprogram which is stored in a computer readable format in a recordingmedia such as CDROM, RAM, ROM, floppy disk, hard disk, magneto-opticaldisk, etc. Since this process is well known to those skilled in the art,its detailed explanation will be omitted hereinafter.

In accordance with the present invention, when the plurality of nodestry to send and receive data to each other in the communication networkenvironment consisting of the plurality of nodes and one commoncommunication bus, by making each node send and receive data accordingto its priority whenever it tries to send and receive the data, it ispossible to improve ineffective message transmission of thetime-triggered scheme and also advance a defect of the event-triggeredscheme in which the transmission of messages having lower priorities canbe indefinitely delayed according to the dynamic priority adjustment.

The present application contains subject matter related to Korean patentapplication No. 2004-0097709, filed with the Korean IntellectualProperty Office on Nov. 25, 2004, the entire contents of which isincorporated herein by reference.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

1. A dynamic priority based message transmitting apparatus, whichcomprises: a minimum priority storing means for recording priorities ina communication network environment consisting of a plurality of nodesand recording the lowest priority among the priorities; a communicationbus monitoring means for monitoring a communication bus and transmittinga corresponding message when the communication bus is in an idle state;a message collision solving means for solving message collision bymonitoring message transmission when messages are transmitted from theother nodes at the same time, comparing a corresponding priority andthose of the other nodes and, according to the comparison result,transmitting the corresponding message if the corresponding priority ishigher than those of the other nodes while not transmitting thecorresponding message if the corresponding priority is lower than thoseof the other nodes; a message filtering means for performing thefiltering by judging whether or not a corresponding node has to processthe corresponding message based on an identifier of the correspondingmessage; and a priority adjusting means for adjusting the priority ofthe corresponding node according to a predefined rule.
 2. The dynamicpriority based message transmitting apparatus of claim 1, wherein thepriority adjusting means operates based on a local priority adjustingscheme in which the priority adjusting means in each node adjusts thepriority of the corresponding node every fixed time, or a globalpriority adjusting scheme in which the priority of the correspondingnode is adjusted only when receiving a priority adjusting message from aglobal priority adjusting device.
 3. The dynamic priority based messagetransmitting apparatus of claim 1, wherein a message has: a messageheader containing a message identifier and other control information;and a message body containing practical data to be transmitted.
 4. Thedynamic priority based message transmitting apparatus of claim 3,wherein the plurality of nodes lower their priorities by one step whenreceiving the priority adjusting message from the global priorityadjusting device or every predetermined time, and a node having thelowest priority becomes to have the highest priority by dynamicalpriority change of each node, so that the priority of said each nodereturns to its initial value after repeating the priority changeoperation N times and said each node can have the highest priority onetime if receiving the priority adjusting message (N-1) times to therebysend its message without waiting indefinitely.
 5. The dynamic prioritybased message transmitting apparatus of claim 4, wherein the globalpriority adjusting device includes: a static/dynamic priority adjustingtable; and a priority adjusting message transmitting unit for deliveringthe priority adjusting message, wherein the priority adjusting messagetransmitting unit continuously sends the priority adjusting message in apreset time period and the preset time being stored in the staticpriority adjusting table while it sends the priority adjusting messagein an irregular period varying according to a time stored in the dynamicpriority adjusting table and said time is differently set to each nodeon a communication network and stored in the dynamic priority adjustingtable.
 6. A global priority adjusting apparatus using a dynamic prioritybased message transmitting device, which comprises: a static/dynamicpriority adjusting table; and a priority adjusting message transmittingunit for delivering a priority adjusting message, wherein the priorityadjusting message transmitting unit continuously sends the priorityadjusting message in a preset time period and the preset time beingstored in the static priority adjusting table while it sends thepriority adjusting message in an irregular period changing according toa time stored in the dynamic priority adjusting table and said time isdifferently set to each node on a communication network and stored inthe dynamic priority adjusting table.
 7. A dynamic priority messageprocessing method, which comprises the steps of: (a) assigning apriority and a minimum priority to each node in a communication networkenvironment consisting of a plurality of nodes; (b) checking out whetheror not a current communication bus is available according to a messagetransmission request from a user and, as a result of the comparison,transmitting a corresponding message if the communication bus isavailable; (c) detecting message collision if more than two nodestransmit messages at the same time through a message collision solvingunit and transmitting a message of a node having the highest priorityafter comparing priorities of said nodes; (d) receiving only a messagewhich should be processed at a corresponding node receiving said messageby using a filtering function after the corresponding node checksidentifier information of said message; and (e) changing its priorityaccording to a preset time or adjusting the priority after receiving apriority adjusting message from a global priority adjusting device. 8.The dynamic priority message processing method of claim 7, wherein thestep (e) is performed based on a local priority adjusting scheme inwhich a priority adjusting unit in each node adjusts the priority of thecorresponding node every fixed time, or a global priority adjustingscheme in which the priority of the corresponding node is adjusted onlywhen receiving the priority adjusting message from the global priorityadjusting device.
 9. The dynamic priority message processing method ofclaim 7, wherein a message has: a message header containing a messageidentifier and other control information; and a message body containingpractical data to be transmitted.
 10. The dynamic priority messageprocessing method of claim 9, wherein the plurality of nodes lower theirpriorities by one step when receiving the priority adjusting messagefrom the global priority adjusting device or every predetermined time,and a node having the lowest priority becomes to have the highestpriority by a dynamical priority change of each node, so that thepriority of said each node returns to its initial value after repeatingthe priority change operation N times and said each node can have thehighest priority one time if receiving the priority adjusting message(N-1) times to thereby send its message without waiting indefinitely.11. The dynamic priority message processing method of claim 10, whereinthe global priority adjusting device includes: a static/dynamic priorityadjusting table; and a priority adjusting message transmitting unit fordelivering the priority adjusting message, wherein the priorityadjusting message transmitting unit continuously sends the priorityadjusting message in a preset time period and the preset time beingstored in the static priority adjusting table while it sends thepriority adjusting message in an irregular period varying according to atime stored in the dynamic priority adjusting table and said time isdifferently set to each node on a communication network and stored inthe dynamic priority adjusting table.